Parcelable vs Serializable

april 18, 2013

When starting on Android, we all learn that we cannot just pass object references to activities and fragments, we have to put those in an Intent / Bundle.

Looking at the api, we realize that we have two options, we can either make our objects Parcelable orSerializable. As Java developers, we already know of the Serializable mechanism, so why bother with Parcelable?

To answer this, lets take a look at both approaches.

Serializable, the Master of Simplicity

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// access modifiers, accessors and constructors omitted for brevity

publicclassSerializableDeveloper implementsSerializable

String name;

intyearsOfExperience;

List<Skill> skillSet;

floatfavoriteFloat;

staticclassSkill implementsSerializable {

String name;

booleanprogrammingRelated;

}

}

The beauty of serializable is that you only need to implement the Serializable interface on a class and its children. It is a marker interface, meaning that there is no method to implement, Java will simply do its best effort to serialize it efficiently.

The problem with this approach is that reflection is used and it is a slow process. This mechanism also tends to create a lot of temporary objects and cause quite a bit of garbage collection.

According to google engineers, this code will run significantly faster. One of the reasons for this is that we are being explicit about the serialization process instead of using reflection to infer it. It also stands to reason that the code has been heavily optimized for this purpose.

However, it is obvious here that implementing Parcelable is not free. There is a significant amount of boilerplate code and it makes the classes harder to read and maintain.

The methodology

Do an average on 10 separate runs to account for memory allocation, other apps using the cpu, etc

The object under test are the SerializableDeveloper and the ParcelableDeveloper shown above

Test on multiple devices – android versions

LG Nexus 4 – Android 4.2.2

Samsung Nexus 10 – Android 4.2.2

HTC Desire Z – Android 2.3.3

The results

Nexus 10

Serializable: 1.0004ms, Parcelable: 0.0850ms – 10.16x improvement.

Nexus 4

Serializable: 1.8539ms – Parcelable: 0.1824ms – 11.80x improvement.

Desire Z

Serializable: 5.1224ms – Parcelable: 0.2938ms – 17.36x improvement.

There you have it: Parcelable is more than 10x faster than Serializable! It is also interesting to note that even on a Nexus 10, a pretty simple object can take about 1 millisecond to go through a full serialize/deserialize cycle.

The Bottom Line

If you want to be a good citizen, take the extra time to implement Parcelable since it will perform 10 times faster and use less resources.

However, in most cases, the slowness of Serializable won’t be noticeable. Feel free to use it but remember that serialization is an expensive operation so keep it to a minimum.

If you are trying to pass a list with thousands of serialized objects, it is possible that the whole process will take more than a second. It can make transitions or rotation from portrait to lanscape feel very sluggish.